A typical cone crusher comprises a frame provided with a main shaft and an outer crushing blade. A conical inner crushing blade is fitted on the main shaft and is movable on the main shaft with respect to the outer crushing blade so that a forced stroke is produced in the crushing chamber between the crushing blades.
In crushers of prior art, it is possible to change the stroke by changing the eccentricity of the path of the crushing cone. For example, publication U.S. Pat. No. 6,213,418 discloses a crusher, in which the eccentricity of the path is affected by changing the mutual positions of the outer and inner cylinders on the eccentric shaft. In this arrangement, the crusher must be disassembled for an adjustment, for which reason the adjustment takes time.
Publication WO 00/78457 discloses a crusher in which the stroke of the first crushing blade can be adjusted during the use of the crusher (i.e. without disassembling the crusher). In order to make this possible the eccentric shaft of the crusher has been constituted of inner eccentric shaft and outer eccentric shaft. The inner eccentric shaft is inside the outer eccentric shaft and these eccentric shafts are arranged to be turnable in respect of each other to change the amount of eccentricity of the eccentric shaft and the eccentric path of the main shaft. The mutual movement of the first and second eccentric shafts is accomplished by gear transmissions comprising a first cog wheel attached to the outer eccentric shaft and second cog wheel attached to the inner eccentric shaft, and a turning mechanism for turning the first cog wheel and the second cog wheel in respect of each other, in all embodiments of the crusher described in this publication the main shaft of the crusher is supported (in horizontal direction) by the inner and outer eccentric shafts being around the lower part of the main shaft and being supported by bearings fitted between the lower part of the frame of the crusher and the outer eccentric shaft. The first crushing blade is attached in all embodiments to the main shaft to the upper part of the main shaft so that the eccentric shaft leaves below (outside) the first crushing blade. It is not so great disadvantage in case of the crusher being provided supporting bearings at two points i.e. in the lower end and the upper end of the main shaft. However in such crushers having no upper supporting bearing for the main shaft it is more disadvantageous since forces formed by material to be crushed cause greater bending moments longer the distance between the bearings of the main shaft and the upper end of the first crushing blade. In addition in all type of crushers with this kind of construction increases the height of the crusher and thus makes it heavier and more space consuming.